A new study from the New England Journal of Medicine found that protection against whooping cough drops by 40 percent a year after the fifth and final dose of the vaccine series is administered.

Study author Dr. Nicola Klein, co-director of the Kaiser Permanente Vaccine Study Center, told HealthDay,"If we estimate that after the fifth dose of vaccine, protection is at 95 percent, protection would decrease to 71 percent after five years."

The vaccine for pertussis, called DTaP, is given in a five-dose schedule from infancy to six years of age. A booster during adolescence is recommended, as is one in adulthood, although many people choose not to or don’t know to get it.

In 2010, almost 28,000 Americans contracted pertussis, according to the CDC. The disease can be deadly in babies who haven’t yet been vaccinated.

Klein said that reformulating the current vaccine or developing a new one is something that should be considered. However, for now in addition to children receiving the shot as typically administered, they should also get a booster vaccine at 11 or 12 years old, once the initial cycle’s effectiveness could have faded.

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